CN102542166A - Dynamic fault tree analysis method for system with correlated failure mode - Google Patents

Abstract

The invention relates to a dynamic fault tree analysis method for a system with a correlated failure mode, comprising the following steps of: 1, defining the correlated failure mode; 2, defining a correlated failure gate corresponding to the correlated failure mode; 3, solving the correlated failure gate through a Markov chain; 4, establishing a dynamic fault tree model of the system through the correlated failure gate; and 5, solving the dynamic fault tree model of the system to obtain the reliability of the system. The dynamic fault tree analysis method has the beneficial effects that the reliability of the correlated failure mode can be quantitatively calculated through analyzing and calculating the reliability of the correlated failure mode, so that the reliability of the system can be accurately obtained, and the maintenance and replacement costs of parts can be effectively reduced on the premise of ensuring the reliability of the system.

Description

Dynamic fault tree analytical approach with inefficacy associative mode system

Technical field

The invention belongs to the fail-safe analysis technical field of electronic product, specifically is a kind of towards the dynamic fault tree analytical approach with inefficacy associative mode system.

Background technology

Reliability engineering has been widely used in each engineering field; Aircraft industry is a kind of high-precision comprehensive industry; Some aeronautical product can be related to the life security of aircrew and passenger; Some aeronautical product then can concern the success or failure of the whole war situation, so reliability engineering seems particularly important for aircraft industry, and the reliability of aeronautical product is mainly studied the technical measures of ultimate principle, method and the assurance product reliability level of reliability.

In recent years, unmanned plane seems more and more important in the effect of aviation field.Since the Gulf War in 1991, many countries all place the status of first developing to it, competitively develop and equip, and have worldwide started the upsurge of development unmanned plane.Though the unmanned plane superior performance, advanced technology, because the influence of the factors such as dexterity of the overlength property of the complicacy of self system, Remote distance and operative technique, the unmanned plane major accident frequently occurs.The generation of these unmanned plane accidents has proposed stern challenge to unmanned plane fail-safe analysis and design.

Fault tree is widely used in fail-safe analysis.Fault tree analysis is the graphic method that logic is arranged that a kind of combination through failure event, order are assessed the probability of happening of top event.In the fault tree analysis method,, describe with boolean logic gate (with door or door and voting door) for the syntagmatic between the failure event; For the ordinal relation between the failure event, with dynamic logic gate (preferential and door, order associated gate, function associated gate, cold standby door, Hot Spare door and warm spare door) expression.Have only the fault tree of boolean logic gate to be called the static failure tree, the fault tree that contains dynamic logic gate is called the dynamic fault tree.

Existing Mechatronic Systems is carried out in the fail-safe analysis; We find a kind of failure mechanism of system; When can causing the crash rate of miscellaneous part, the inefficacy of parts changes (in the Circuits System that constitutes like two parallel resistor; The open failure of one of them resistance will cause the raising of the crash rate of another resistance); We are defined as the inefficacy associative mode with this failure mechanism, and existing dynamic fault tree analytical approach can't be carried out quantitative test to this failure mechanism, and the quantitative test of inefficacy associative mode is had important meaning to the fail-safe analysis of system: the reliability of analytic system accurately; Can under the prerequisite that guarantees system reliability, effectively reduce the maintain and replace cost.

Summary of the invention

The objective of the invention is to carry out this defective of quantitative test to the inefficacy associative mode, proposed a kind of dynamic fault tree analytical approach with inefficacy associative mode system in order to overcome existing dynamic fault tree analytical approach.

Technical scheme of the present invention: have the dynamic fault tree analytical approach of inefficacy associative mode system, comprise step:

Step 1: definition inefficacy associative mode;

Step 2: the corresponding inefficacy associated gate of definition inefficacy associative mode;

Step 3: the inefficacy associated gate is found the solution through Markov (Markov) chain;

Step 4: the dynamic fault tree-model of setting up system through the inefficacy associated gate;

Step 5: the dynamic fault tree-model of solving system obtains system dependability.

In the above-mentioned steps 3 the inefficacy associated gate is found the solution the following formula of employing:

$F_s\left(t\right)=\left\{\begin{array}{cc}1-e^{-2\mathrm{\α\λt}}+c\left(\frac{2\mathrm{\α}}{2\mathrm{\α}-1}\right)(e^{-2\mathrm{\α\λt}}-e^{-\mathrm{\λt}}),& \mathrm{\α}\≠0.5\\ 1-(1+\mathrm{c\λt})e^{-\mathrm{\λt}},& \mathrm{\α}=0.5\end{array}\right..$

In the formula, F _s(t) the failure probability function of expression system; α is the derate factor, and λ is the crash rate of parts, and t is the time; C is a coverage coefficient; When α=0.5th,, the crash rate correction factor when expression parts derate is used is 0.5, the crash rate correction factor the when use of parts derate is represented in α ≠ 0.5 is not equal to 0.5.

Beneficial effect of the present invention is: pass through fail-safe analysis and calculating to the inefficacy associative mode among the present invention; The reliability to the inefficacy associative mode that can be quantitative is calculated; Thereby can obtain the fiduciary level of system accurately; Under the prerequisite that guarantees system reliability, effectively reduce the maintain and replace cost of parts.

Description of drawings

The synoptic diagram of the embodiment that Fig. 1 method of the present invention is directed against.

Fig. 2 step 2 inefficacy of the present invention associated gate synoptic diagram.

The Markov chain synoptic diagram that Fig. 3 step 3 inefficacy of the present invention associated gate is corresponding.

The fault tree model synoptic diagram of Fig. 4 embodiments of the invention.

Fig. 5 main flow chart of the present invention.

Embodiment

Below in conjunction with accompanying drawing technical scheme of the present invention is done detailed explanation.

As shown in Figure 5, the dynamic fault with inefficacy associative mode system is set analytical approach, comprises step:

Step 1: definition inefficacy associative mode.

The inefficacy associative mode is meant that the inefficacy of parts can cause that the crash rate of miscellaneous part changes.Crash rate is meant that work arrives the product that a certain moment do not lose efficacy as yet, this constantly after, the probability that lost efficacy took place in the unit interval.Generally crash rate is designated as λ, it also is the function of time t, so also be designated as λ (t), λ (t) is called as the crash rate function, is also referred to as failure rate function or risk function sometimes.

As shown in Figure 1 is a specific embodiment of the present invention; Among Fig. 1; Flight-control computer (abbreviation flight control computer) has two groups of power supplys: power source special 1 and power source special 2; This is the airborne energy power supply system of classics, and power source special adopts two remaining designs to supply power simultaneously to flight-control computer, improves the purpose of system reliability.In the present embodiment, the crash rate of definition power source special 1 is λ ₁, the crash rate of power source special 2 is λ ₂, after power source special 1 lost efficacy, the crash rate λ of power source special 2 ₂Can significantly uprise, vice versa.

Step 2: the corresponding inefficacy associated gate of definition inefficacy associative mode.

In this step; In the dynamic fault tree-model, define a kind of new fault tree synthesis and come the inefficacy associative mode is carried out quantitative test, be called inefficacy associated gate (FADEP; Failure Dependency); As shown in Figure 2, the inefficacy associated gate can have two elementary events or non-deploy events as incoming event, an outgoing event.α is a derate factor vector, i the element α of α _i(α _i∈ [0,1]) the derate factor of the individual input of expression i (i=1,2). the derate factor is the correction factor of the crash rate of parts when derate is used.When two derate factors equated, α deteriorated to a scalar from vector.And if only if when two incoming events all take place, and outgoing event takes place.Make the crash rate of λ (t), then the crash rate of the parts of α λ (t) expression derate use for the normal parts that use.

Step 3: the inefficacy associated gate is found the solution through Markov (Markov) chain.

As shown in Figure 3; The failure probability of system (being different from crash rate) is made up of two parts: inefficacy takes place to cover and (caused thrashing when taking place immediately if certain loses efficacy in a power source special; This inefficacy is called can not cover inefficacy) probability and the generation of power source special elder generation can cover inefficacys and (not cause thrashing during generation if certain lost efficacy; This inefficacy is called can cover inefficacy) probability, another takes place subsequently to cover and lost efficacy or can cover the probability of inefficacy.

If the inefficacy obeys index distribution of parts (like power source special) can be carried out modeling to both of these case through the Markov chain.

The analytic solution of inefficacy associated gate are as follows:

$F_s\left(t\right)=\left\{\begin{array}{cc}1-e^{-2\mathrm{\α\; \λ\; t}}+c\left(\frac{2\mathrm{\α}}{2\mathrm{\α}-1}\right)(e^{-2\mathrm{\α\; \λ\; t}}-e^{-\mathrm{\λ\; t}}),& \mathrm{\α}\≠0.5\\ 1-(1+\mathrm{C\λ\; t})e^{-\mathrm{\λ\; t}},& \mathrm{\α}=0.5\end{array}\right.$ Formula (1)

In the formula, F _s(t) the failure probability function of expression system, subscript s is the abbreviation of the svstem of system, α is the derate factor; λ is the crash rate of parts, and t is the time, and c is a coverage coefficient; Be a constant, generation can cover the conditional probability when losing efficacy under the expression parts generation failure condition, when α=0.5th; Crash rate correction factor when expression parts derate is used is 0.5, and the crash rate correction factor the when use of parts derate is represented in α ≠ 0.5 is not equal to 0.5.

Step 4: the dynamic fault tree-model of setting up system through the inefficacy associated gate.

In the present embodiment, the fault tree model with inefficacy associated gate (FADEP) of this system (airborne energy power supply system) correspondence is as shown in Figure 4.Among the figure, top event (can't power supply be provided to flight-control computer) is the outgoing event of inefficacy associated gate.Two elementary events (power source special 1 lost efficacy, and power source special 2 lost efficacy) are as the incoming event of inefficacy associated gate.When two power source specials were worked simultaneously, they were used by derate, and corresponding failure rate is α λ (t).During one of them open circuit (can cover inefficacy), another failure rate becomes λ (t).And if only if when two incoming events all take place, outgoing event, and promptly top event just takes place.

Step 5: the dynamic fault tree-model of solving system obtains system dependability.

In the present embodiment, each parameter of system's (airborne energy power supply system) is shown in Fig. 1 table 1., the fiduciary level 1-F of system _s(t) be 0.994.

Table l thrashing parameter

Be t=10 task time ⁴Hour the data of table 1 in the table 1 are brought in the formula (1) of step 3 and to obtain F _s(t)=0.006, thus obtain the fiduciary level 1-F of system _s(t)=0.994.

Above-described specific embodiment; The object of the invention, technical scheme and beneficial effect have been carried out further explain; Should be understood that protection scope of the present invention is not limited to such special statement and embodiment; All within spirit of the present invention and principle, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (2)

1. have the dynamic fault tree analytical approach of inefficacy associative mode system, comprise step:

Step 1: definition inefficacy associative mode;

Step 2: the corresponding inefficacy associated gate of definition inefficacy associative mode;

Step 3: the inefficacy associated gate is found the solution through Markov (Markov) chain;

Step 4: the dynamic fault tree-model of setting up system through the inefficacy associated gate;

Step 5: the dynamic fault tree-model of solving system obtains system dependability.

2. according to the described dynamic fault tree analytical approach of claim l, it is characterized in that, in the above-mentioned steps 3 the inefficacy associated gate found the solution the following formula of employing with inefficacy associative mode system:

$F_s\left(t\right)=\left\{\begin{array}{cc}1-e^{-2\mathrm{\α\λt}}+c\left(\frac{2\mathrm{\α}}{2\mathrm{\α}-1}\right)(e^{-2\mathrm{\α\λt}}-e^{-\mathrm{\λt}}),& \mathrm{\α}\≠0.5\\ 1-(1+\mathrm{c\λt})e^{-\mathrm{\λt}},& \mathrm{\α}=0.5\end{array}\right..$

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